- Influence of the N→Ru Coordinate Bond Length on the Activity of New Types of Hoveyda-Grubbs Olefin Metathesis Catalysts Containing a Six-Membered Chelate Ring Possessing a Ruthenium-Nitrogen Bond
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An efficient approach to the synthesis of new types of Hoveyda-Grubbs catalysts containing an N→Ru bond in a six-membered chelate ring is proposed. The synthesis of the organometallic compounds is based on the interaction of ready accessible 2-vinylbenzylamines and 1,3-bis(2,4,6-trimethylphenyl)-2-trichloromethylimidazolidine ligands with dichloro(3-phenyl-1H-inden-1-ylidene)bis(tricyclohexylphosphane)ruthenate, and it afforded the target ruthenium complexes in 70-80% yields. Areas of practical utility and potential applications of the obtained chelates were highlighted by tests of the catalysts in different olefin cross-metathesis (CM) and ring-closing-metathesis (RCM) reactions. These experiments revealed a high catalytic performance (up to 10-2 mol %) of all the synthesized structures in a broad temperature range. The structural peculiarities of the resultant ruthenium catalysts were thoroughly investigated by X-ray crystallography, which allowed making a reliable correlation between the structure of the metallo-complexes and their catalytic properties. It was proved that the bond length between ruthenium and nitrogen in the six-membered chelate ring has the greatest effect on the stability and efficiency of the catalyst. As a rule, the shorter and stronger the N→Ru bond, the higher the stability of the complex and the worse its catalytic characteristics. In turn, the coordination N→Ru bond length can be finely tuned and varied over a wide range of values by changing the steric volume of the cyclic substituents at the nitrogen atom, which will make it possible, as appropriate, to obtain in the future metal complexes with predictable stability and the required catalytic activity. Also, it was found that complexes in which the nitrogen atom is included in the morpholine or isoquinoline rings are the most efficient catalysts in this series. An attempt to establish a correlation between the N→Ru bond length and the 1H and 13C chemical shifts in the Ru═CH fragment has been made.
- Alekseeva, Kseniia A.,Antonova, Alexandra S.,Grigoriev, Mikhail S.,Kumandin, Pavel A.,Nikitina, Eugeniya V.,Novikov, Roman A.,Polyanskii, Kirill B.,Sinelshchikova, Anna A.,Vasilyev, Kirill A.,Zubkov, Fedor I.
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Read Online
- Palladium(II)-catalyzed isomerization of (Z)-1,4-diacetoxy-2-butene: Solvent effects
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The isomerization of (Z)-1,4-diacetoxy-2-butene (1) catalyzed by PdCl 2(MeCN)2 was studied in THF and DMF. The reaction occurs more rapidly in THF than in DMF, but in both solvents it did not proceed to complete consumption of the substrate and led to a mixture of 1, (E)-1,4-diacetoxy-2-butene (2), and 1,2-diacetoxy-3-butene (3). The formation of 2 is more favored in DMF than in THF. The reactivity of 1 and the solvent effect differ strongly from those previously obtained with Pd(PPh 3)4 as the catalyst. Interpretations are provided for the crucial role of the nature of both solvent and intermediates on the course of the isomerizations. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
- Zawisza, Anna Maria,Bouquillon, Sandrine,Muzart, Jacques
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Read Online
- Effect of a proximal oxygen substituent on the efficacy of ruthenium-catalyzed cross-metathesis and RCM
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Ruthenium-catalyzed cross-metathesis of various derivatives of 1,2-dihydroxy-3-butene reveals that cyclic acetals are best suited as substrates compared to acyclic diethers or diacetates, while RCM is relatively insensitive to the presence of allylic or homoallylic hydroxy or acetoxy groups.
- Maishal, Tarun K,Sinha-Mahapatra, Dilip K,Paranjape, Kavita,Sarkar, Amitabha
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Read Online
- Palladium(0)-catalyzed isomerization of (Z)-1,4-diacetoxy-2-butene - Dependence of η1- or η3-allylpalladium as a key intermediate on the solvent polarity
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In the presence of Pd(PPh3)4, (Z)-1,4-diacetoxy-2-butene is selectively isomerized to (E)-1,4-diacetoxy-2-butene in THF while both (E)-1,4-diacetoxy-2-butene and 1,2-diacetoxy-3-butene are obtained in DMF. Evidence to support the involvement of an η1-allylpalladium in the former solvent and of a cationic η3-allylpalladium in the latter as the keys intermediates is presented.
- Bouquillon, Sandrine,Muzart, Jacques
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Read Online
- Preparation method of 4-acetoxy-2-methyl-2-butenal
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The invention discloses a method for preparing 4-acetoxyl-2-methyl-2-butenal, and the method comprises the following steps: forming a catalyst system by using a cobalt acid complex and a metal chloride, mixing 4-acetoxyl-2-methylene butyraldehyde (III) with hydrogen, and performing heating to react to obtain the 4-acetoxyl-2-methyl-2-butenal. In the prior art, precious metal needs to be used as a catalyst in the step, and the yield and the selectivity are not high. The method does not need to use a noble metal catalyst, is lower in cost, high in double-bond isomerization reaction speed and high in reaction yield, and is easy to realize industrial production.
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Paragraph 0064-0067
(2021/08/11)
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- Process for preparation of 4-acetoxy-2-methyl-2-butene-1-aldehyde and intermediates thereof
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The invention relates to the technical field of organic synthesis, and discloses a method for preparing 4-acetoxy-2-methyl-2-butene-1-aldehyde and an intermediate thereof. The method comprises the following steps: (1) in the presence of an esterification reagent, carrying out esterification reaction on 1, 4-butenediol to obtain 1, 4-butenediol diacetate; (2) in the optional presence of a first catalyst, carrying out an isomerization reaction on the 1, 4-butenediol diacetate to obtain 3, 4-diacetoxy-1-butene; (3) in the presence of a phosphorus-containing ligand and a rhodium catalyst and/or a cobalt catalyst, carrying out hydroformylation reaction on the 3, 4-diacetoxy-1-butene, carbon monoxide and hydrogen to obtain 2-methyl-3, 4-diacetoxy-1-butyraldehyde; (4) in the optional presence of a third catalyst, carrying out an elimination reaction on the 2-methyl-3, 4-diacetoxyl-1-butyraldehyde to obtain the 4-acetoxyl-2-methyl-2-butene-1-aldehyde. The method provided by the invention has the advantages of mild reaction conditions, environmental friendliness and high yield.
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Paragraph 0055-0056; 0065-0066; 0072-0073; 0079-0080
(2021/06/09)
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- Protection of COOH and OH groups in acid, base and salt free reactions
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We report an iron-catalyzed general functional group protection method with inexpensive reagents. This environmentally benign process does not use acids or bases, and does not produce waste products. Further purification beyond filtration and evaporation is, in most cases, unnecessary. Free COOH and OH groups can be protected in a one-pot reaction.
- Zhu, Xiaotao,Qian, Bo,Wei, Rongbiao,Huang, Jian-Dong,Bao, Hongli
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supporting information
p. 1444 - 1447
(2018/04/12)
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- Stereoselective Dynamic Cyclization of Allylic Azides: Synthesis of Tetralins, Chromanes, and Tetrahydroquinolines
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This report describes the stereoselective synthesis of 3-azido-tetralins, -chromanes, and -tetrahydroquinolines via a tandem allylic azide rearrangement/Friedel-Crafts alkylation. Exposure of allylic azides with a pendant trichloroacetimidate to catalytic quantities of AgSbF6 proved optimal for this transformation. This cascade successfully differentiates the equilibrating azide isomers, providing products in excellent yield and selectivity (>25 examples, up to 94% yield and >25:1 dr). In many cases, the reactive isomer is only a trace fraction of the equilibrium mixture, keenly illustrating the dynamic nature of these systems. We demonstrate the utility of this process via a synthesis of hasubanan.
- Porter, Matthew R.,Shaker, Rami M.,Calcanas, Cristian,Topczewski, Joseph J.
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supporting information
p. 1211 - 1214
(2018/02/09)
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- Preparation method of 3,4-diacetoxy-1-butene
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The invention discloses a preparation method of 3,4-diacetoxy-1-butene. The preparation method comprises steps as follows: an esterification step: 1,4-butylene glycol and acetic acid are subjected to an esterification reaction in the presence of acid, a solution containing 1,4-diacetoxy-2-butene and acetic acid is obtained, acetic acid is removed and 1,4-diacetoxy-2-butene is obtained; an isomerization step: cuprous catalysts are added to 1,4-diacetoxy-2-butene obtained in the esterification step, the mixture is heated for an isomerization rearrangement reaction, and a mixed solution containing 3,4-diacetoxy-1-butene is obtained; a purification step: the mixed solution obtained in the isomerization step is purified, and 3,4-diacetoxy-1-butene is obtained. The preparation method adopts easy-to-realize reaction conditions and has the characteristic of high yield.
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Paragraph 0039; 0052; 0058; 0064; 0074-0077
(2018/04/01)
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- OLEFIN METATHESIS CATALYSTS
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This invention relates generally to metathesis catalysts and the use of such catalysts in the metathesis of olefins and olefin compounds, more particularly, in the use of such catalysts in Z and E selective olefin metathesis reactions. The invention has utility in the fields of organometallics and organic synthesis.
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Page/Page column 86; 87
(2017/07/06)
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- Allylic C–H acetoxylation of terminal alkenes over TiO2 supported palladium nanoparticles using molecular oxygen as the oxidant
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A method for synthesizing linear allylic acetates from terminal alkenes over TiO2 supported Pd nanoparticles (NPs) has been developed, in which O2 serves as the sole oxidant. Good catalytic activity was performed when using allylbenzene as a substrate and the catalyst can be reused at least five times without activity losing. The catalytic system has a broad substrate scope including transformation of 1,3-butadiene into 1,4-diacetoxy-2-butene, which is an important industrial intermediate for production of 1,4-butanediol. In contrast to previous reports that the Pd-catalyzed allylic acetoxylation is generally promoted by PdII species, the XAFS measurements suggest that this reaction is catalyzed over Pd0 NPs. Additionally, XPS analysis of the catalyst confirms the interaction between Pd and TiO2, which probably promote the initial catalytic procedure.
- Zhang, Zhenzhong,Wu, Qixun,Hashiguchi, Taishin,Ishida, Tamao,Murayama, Haruno,Tokunaga, Makoto
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- Biomass derived β-cyclodextrin-SO3H as a solid acid catalyst for esterification of carboxylic acids with alcohols
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A novel β-cyclodextrin-SO3H carbon based solid acid catalyst was prepared in a convenient and ecofriendly manner and was characterized using FTIR, PXRD, EDAX and NH3TPD to illustrate that the carbon material has been functionalized with -SO3H, -COOH and -OH groups. The catalyst was studied for esterification of various carboxylic acids and alcohols under solvent free conditions and showed excellent catalytic performance and gave good yields of esters in the range 78-99% at 70°C. No solvent was used either for catalyst preparation nor for esterification reaction. The catalyst can be easily recovered by simple filtration and reused for subsequent three runs without any significant impact on yields of products. The main advantage of this methodology is easy and ecofriendly catalyst preparation, easy catalyst separation, practical simplicity, safe reaction conditions, recyclable catalyst and high product yields.
- Thombal, Raju S.,Jadhav, Amol R.,Jadhav, Vrushali H.
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p. 12981 - 12986
(2015/02/19)
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- Comparison of reactivity in the cross metathesis of allyl acetate-derivatives with oleochemical compounds
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The metathesis of unsaturated oleochemicals is an excellent tool for generating α,ω-difunctional substrates, which are useful intermediates for polymer synthesis. This article describes the cross metathesis of allyl acetate and cis-1,4-diacetoxy-2-butene with methyl 10-undecenoate and methyl oleate, which are oleochemical key substrates. Detailed optimizations led to high conversion rates and yields of the desired products under mild reaction conditions by using a low concentration of commercially available homogeneous ruthenium catalysts.
- Behr, Arno,Toepell, Stephanie
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p. 603 - 611
(2015/03/04)
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- METHOD FOR ISOMERIZING ALLYL COMPOUND
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Catalyst for isomerization of allyl compound in method, catalyst by restraining degradation caused, low catalyst levels usage in high yield isomer make it possible to obtain a an industrially advantageous method provides for isomerization of allyl compounds. In the presence of catalyst, raw material allyl compound corresponding allyl compound as isomerizing method, before isomerization using catalyst raw material allyl compounds organic phosphorus compound-containing solution is characterized by contacting the isomerization method.
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Paragraph 0119; 0120
(2017/01/02)
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- ((2S,4R)-4,6-dihydroxytetrahydro-2H-pyran-2-yl)methyl carboxylate and process for the production thereof
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The present invention relates to ((2S,4R)-4,6-dihydroxytetrahydro-2H-pyran-2-yl)methyl carboxylates and a process for the production thereof. Furthermore, the present invention relates to a process for the production of statins and in particular of Rosuvastatin and derivates thereof, wherein the above mentioned compounds are used as intermediates.
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(2013/04/10)
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- PROCESS FOR PRODUCING ESTER COMPOUND HAVING a,?-UNSATURATED BOND
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A process for producing an α,β-unsaturated bond-containing ester compound, comprising: reacting an internal olefin or a cyclic olefin having one carbon-carbon double bond or more at a position other than terminals of a molecule thereof (the internal olefin and the cyclic olefin may each contain a hetero atom) with a carboxylic acid in an amide-based solvent in the presence of a palladium catalyst, a base, and molecular oxygen, thereby bonding a carboxyl group of the carboxylic acid to at least one of carbon atoms constituting the carbon-carbon double bond and carbon atoms at allylic positions of the internal olefin or the cyclic olefin, to obtain an ester compound having an α,β-unsaturated bond, the amide-based solvent being represented by the following formula (1): (in the formula (1), R1 represents an alkyl group having 1 to 4 carbon atoms; R2 and R3 each independently represent an alkyl group having 1 to 4 carbon atoms or an aryl group; and when R1 and R2 are alkyl groups, R1 and R2 may be bonded to each other to form a ring structure).
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(2013/02/27)
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- Total synthesis of haminol A: An analysis of vinylpyridine metathesis reactivity
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The total synthesis of haminol A has been completed featuring a masked-alkene metathesis reaction followed by bis-acyloxysulfone elimination to install the 1,3,8-triene subunit. During the course of our synthesis, the metathesis reactivity of 3-vinylpyridine was evaluated and our data suggest the rapid formation of a ruthenium pyridylalkylidene that no longer participates in productive metathesis. A chemotaxis assay using Caenorhabditis elegans demonstrated that haminol A produced an avoidance response from this organism.
- Storvick, Jennifer M.,Ankoudinova, Evgenia,King, Brianne R.,Van Epps, Heather,O'Neil, Gregory W.
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scheme or table
p. 5858 - 5861
(2011/12/14)
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- Mixed isobutylphobane/n-heterocyclic carbene ruthenium- Indenylidene complexes: Synthesis and catalytic evaluation in olefin metathesis reactions
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Two new second generation ruthenium(II) dichloride-indenylidene complexes [RuCl2(9- isobutylphosphabicyclo [3.3.1]nonane) (NHC)(3-phen- yl-1-indenylidene)], where NHC=1,3-bis(2,4,6-trimethylphenyl) imidazolin-2-ylidene (SIMes) or its unsaturated imidazol-2-ylidene analogue (IMes), were isolated in high yields upon heating a tetrahydrofuran (THF) solution of the diphosphane complex [RuCl2(isobutylphobane) 2(3-phenyl-1-indenylidene)]with a two-fold excess of the corresponding imidazol- (in)ium-2-carboxylate zwitterions. Both products were characterized by 1H, 13C, and 31P NMR spectroscopy, and the molecular structure of [RuCl2(isobutylphobane) (SIMes)(3-phenyl-1-indenylidene)]was determined by X-ray diffraction analysis. A close inspection of the packing structure revealed the presence of different types of intra- and intermolecular interactions that enhanced the global stability of the crystals, while low temperature NMR experiments showed the existence of two distinct rotational isomers due to the unsymmetrical nature of the phobane ligand. The catalytic activity of both compounds was assessed in olefin metathesis using benchmark ring-opening metathesis polymerization, ring-closing metathesis (RCM), and cross-metathesis reactions, and compared with those of related first and second generation ruthenium-benzylidene and indenylidene catalyst precursors. Kinetic studies confirmed the high thermal stability of the mixed isobutylphobane/ N-heterocyclic carbene complexes, which suffered from a slow initiation efficiency compared to other catalytic systems based on the tricyclohexylphosphane ligand. However, the remarkable robustness of [RuCl2(isobutylphobane) (SIMes)(3-phenyl-1- indenylidene)]was beneficial for performing the RCM of diethyl 2,2-bis(2-methylallyl)malonate. Monitoring the formation of the ruthenium-methylidene active species [RuCl 2(isobutylphobane)- (SIMes) (=CH2)]derived from this precursor further demonstrated its ability to sustain long reaction times and high temperatures required to carry out the RCM of tetrasubstituted olefins.
- Sauvage, Xavier,Zaragoza, Guillermo,Demonceau, Albert,Delaude, Lionel
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supporting information; experimental part
p. 1934 - 1948
(2010/11/05)
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- METHOD FOR THE SYNTHESIS OF 4-ALKOXY-, 4-HYDROXY- AND 4-ARYLOXY-SUBSTITUTED TETRAHYDRO-FURO[3,4-B]FURAN-2(3H)-ONE COMPOUNDS
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The present invention relates to a method for the synthesis of enantiomerically and diastereomerically enriched 4-alkoxy-, 4-hydroxy- or 4-aryloxy- substituted tetrahydro-furo[3,4-b]furan-2(3H)-ones by aldol coupling of a suitable hydroxyl-protected hydro
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(2009/04/25)
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- Expeditious formation of γ-lactones upon palladium-catalyzed double nucleophilic addition of bis(TMS)ketene acetals to vicinal allylacetates
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Polysubstituted γ-lactones are easily obtained, in one step, upon the interaction of bis(TMS)ketene acetals with vicinal allylic acetates in the presence of catalytic amounts of Pd(PPh3)4.
- Chavez, Cesar Sandoval,Rudler, Henri,Parlier, Andrée,Herson, Patrick
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supporting information; experimental part
p. 5843 - 5846
(2009/04/05)
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- Lewis acid-modified mesoporous alumina: A new catalyst carrier for methyltrioxorhenium in metathesis of olefins bearing functional groups
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Lewis acid-modified mesoporous alumina was found to be an efficient carrier as well as an activator for methyltrioxorhenium (MeReO3) in olefin metathesis reactions. Especially, MeReO3 doped on zinc chloride-modified mesoporous alumina catalyzed the metathesis of olefins with functional groups such as acetoxy, alkoxycarbonyl, acyl, chlorine, and bromine groups under mild conditions. The novel heterogeneous catalytic system promoted the metathesis of not only such functionalized olefins but also simple olefins without double bond migration that was often encountered on strong solid acids. We here present a new methodology for activation of a metal complex with Lewis acidic mesoporous materials in the metathesis reactions. This novel heterogeneous catalyst would be advantageous over conventional one from the viewpoint of environmental and economical organic synthesis.
- Oikawa, Takashi,Masui, Yoichi,Tanaka, Tsunehiro,Chujo, Yoshiki,Onaka, Makoto
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p. 554 - 561
(2008/02/06)
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- Fragment-based drug discovery of carbonic anhydrase II inhibitors by dynamic combinatorial chemistry utilizing alkene cross metathesis
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A fragment-based drug discovery approach to the synthesis and identification of small molecule inhibitors of bovine carbonic anhydrase II (bCA II) is described. The classical bCA II recognition fragment is an aromatic sulfonamide (ArSO2NH2
- Poulsen, Sally-Ann,Bornaghi, Laurent F.
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p. 3275 - 3284
(2007/10/03)
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- A new class of oxygen nucleophiles for regioselective 1,4-addition to butadiene monoxide catalyzed by palladium complexes
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Butadiene monoxide reacts with high regioselectively with anhydrides to give preferentially diesters of 2 buten-1,4-diol in presence of palladium phosphine complexes. Reaction regioselectivity is strongly influenced by the nature of palladium ligand, anhydride and solvent.
- Bianchi, Daniele,Querci, Cecilia,Ricci, Marco,Santi, Roberto
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p. 3081 - 3084
(2007/10/03)
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- Hydrogenolytic reduction of peroxidic ozonolysis products
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A method for the hydrogenolytic reduction of peroxidic ozonolysis products to the corresponding carbonyl compounds in the presence of an inert organic diluting agent and in the presence of a monolith catalyst at hydrogen pressures of 0.01 to 2.0 MPa and at temperatures of -10° to 150° C., and a device for the catalytic hydrogenolysis of chemical compounds which yield uniform, new products by means of hydrogenolysis with hydrogen.
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- ANTIMICROBIAL STRESS COMPOUNDS FROM HYPOCHOERIS RADICATA
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The exudates of hypochoeris radicata leaves stressed with cupric chloride afforded two eudesmane- and guaiane-type sesquiterpenes, and two alkenals, (2E,4E)-6-hydroxyhexadienal and 82E,4E)-hexadienedial (mucondialdehyde).Their structures determined by spectroscopic and synthetic methods. - Key words: Hypochoeris radicata; Asteraceae; stress compound; sesquiterpenoids; alkenals; fungitoxins.
- maruta, Yoshihiko,Fukushi, Yukiharu,Ohkawa, Kaori,Nakanishi, Yuko,Tahara, Satoshi,Mizutani, Junya
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p. 1169 - 1174
(2007/10/02)
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- ACETOXYLATION OF 1,3-BUTADIENE IN THE PRESENCE OF BINARY PLATINOID INTERMETALLIDES
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A study has been made of 1,3-butadiene acetoxylation in the presence of intermetallic catalysts based on platinum group metals and p-elements of the groups II-IV of the periodic system.The selectivity of formation of the desired isomers correlates with the electronegativities of p-elements in Pt(Pd,Rh)-M binary systems.The catalyst activities are governed by the nature of ?- and/or ?-bonding of the substrate with the platinoid component.The effective charge on the central atom determines the probability of outer-sphere attack of acetate ion at corresponding carbon atom in chemisorbed η3-allyl moieties.
- Vekki, A. V. de
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p. 221 - 224
(2007/10/02)
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- Liquid-phase 1,4-Diacetoxylation of Conjugated Dienes with Tellurium(IV) Oxide and Alkali Metal Halides
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Oxidation of buta-1,3-diene, isoprene, and 2,3-dimethylbuta-1,3-diene with tellurium(IV) oxide and lithium bromide in acetic acid affords an isomeric mixture of the corresponding diacetoxyalkenes (1,2- and 1,4-addition products).The product yield and selectivity for 1,4-isomers are high when an excess of LiBr is employed (LiBr/TeO2 = 5-10).The reaction also proceeds in the presence of NaBr, KBr, LiCl, HBr, or I2 in the place of LiBr, but both the selectivity for 1,4-isomers and the product yield are lower.The reaction hardly occurs using LiF, LiI, NaCl, Br2, and NH4Br as a halogen source.The reaction proceeds catalytically with respect to TeO2 to some extent when a re-oxidant such as H2O2 or t-BuOOH is used.In the cases of 2,5-dimethylhexa-2,4-diene, cyclopenta-1,3-diene, cyclohexa-1,3-diene, and cyclo-octa-1,3-diene the results are unsatisfactory in either the product yield or the selectivity for 1,4-isomers.Halogeno- and/or acetoxy-telluriation of a diene followed by acetolysis of the produced C-X (X = halogen) and C-Te bonds are proposed as one of the possible reaction pathways.
- Uemura, Sakae,Fukuzawa, Shin-ichi,Patil, Suresh R.,Okano, Masaya
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p. 499 - 504
(2007/10/02)
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- Stereo-and Regioselective Palladium-Catalyzed 1,4-Diacetoxylation of 1,3-Dienes
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Palladium-catalyzed oxidation of 1,3-dienes in acetic acid using an oxidation system of MnO2 and catalytic amounts of p-benzoquinone selectively gives 1,4-diacetoxy-2-alkenes.The reaction proceeds with high stereo-and regioselectivity, and by ligand control the reaction can be made to take place with either cis or trans 1,4-diacetoxylation across the diene in cyclic systems.Also in an acyclic system the 1,4-relative stereochemistry can be controlled as shown by the stereoselective oxidation of (E,E)- and (E,Z)-2,4-hexadiene to their corresponding dl (>88percent dl) and meso (>95percent meso) diacetates 15 and 18, respectively.Evidence is provided that supports a mechanism involving a trans acetoxypalladation of the conjugated diene to give an intermediate (?-allyl)palladium complex, followed by either a cis or trans attack by acetate on the allyl group.The cis attack is best explained by a cis migration from a (?-allyl)palladium intermediate.The diacetoxylation reaction was applied to the preparation of a key intermediate for the synthesis of dl-shikimic acid.
- Baeckvall, Jan-E.,Bystroem, Styrbjoern E.,Nordberg, Ruth E.
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p. 4619 - 4631
(2007/10/02)
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- DIACETOXYLATION OF CONJUGATED DIENES WITH THALLIUM(III) ACETATE IN ACETIC ACID
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The reaction of conjugated dienes such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2,5-dimethyl-2,4-hexadiene, 1,3-cyclopentadiene, and 1,3-cyclohexadiene with thallium(III) acetate in acetic acid at 10-65 deg C for 0.5-15 hr affords an isomeric mixture of the corresponding diacetoxyalkenes (1,2- and 1,4-addition products) in 10-92 percent yields.The 1,2-addition products are predominantly formed in all cases examined except the case of 1,3-cyclopentadiene.The reaction is assumed to proceed through acetoxythallation and dethallation steps, the latter step being accompanied and/or followed by an attack of acetoxyl group.An initial attack of thallium moiety is proposed to occur mainly at C-1 and C-2 carbons in the cases of linear terminal dienes and cyclic dienes, respectively.
- Uemura, Sakae,Miyoshi, Haruo,Tabata, Akira,Okano, Masaya
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p. 291 - 295
(2007/10/02)
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- SELECTIVE 1,4-DIACETOXYLATION OF CONJUGATED DIENES WITH TELLURIUM(IV) OXIDE
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Oxidation of several linear conjugated dienes with tellurium(IV) oxide and lithium bromide in acetic acid affords an isomeric mixture of the corresponding diacetoxyalkenes (1,2- and 1,4-addition products), 1,4-isomer being highly selectively produced when the ratio of LiBr/TeO2 is 5-10.
- Uemura, Sakae,Fukuzawa, Shin-ichi,Okano, Masaya
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p. 5331 - 5334
(2007/10/02)
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